On the WebReference.com site there's a review recently posted about a PHP-based content management system - a system targeted more towards creating social networking sites than just generic content management.

This CMS has everything a developer needs to create a top of the line social networking site with all the features that users have come to expect from sites like MySpace, Facebook and LinkedIn. [...] Understand that, unlike Elgg, Drupal, Joomla and Dolphin, phpFox is not Open Source (although it is written in PHP). It sells for $300 for a full license, which includes 6 months of free upgrades and support, or you can purchase a monthly license for $39.95, which includes free upgrades and support for each month that is purchased. While $300 may seem like a lot when there are other social networking software packages available for free, as they say, you get what you pay for.

The reviewer goes on to talk about the installation of the software, modules included, core features and some of the more updated, included features like a marketplace module, profile photo cropping, spam filtering, privacy settings for each user and a video module.